In such a composite material, in order for the composite material to exhibit the functions as a composite material, it is desired that CNTs uniformly adhere to the surface of a base material, so as to form a CNT network.
Such a composite material is produced by putting a base material in a solution in which CNTs are dispersed at a nano level (which is also abbreviated as a “CNT nano-dispersion” in the present description), allowing the CNTs to adhere to the surface of the base material while forming a network, then raising the base material from the CNT nano-dispersion, and then drying it.
However, since such CNTs irreversibly aggregate in the CNT nano-dispersion due to the van der Waals force, in order to allow the CNTs to uniformly adhere to the surface of the base material to form a CNT network, it is necessary to add a large amount of dispersant into the CNT nano-dispersion, so that aggregation of the CNTs is prevented and the CNTs are dispersed therein.
Moreover, upon this dispersion, ultrasonic irradiation or stirring is performed as an auxiliary treatment on the CNT nano-dispersion (see Patent Literature 1). A dispersant is required for dispersion of the CNTs, and in general, the dispersant has been used as an essential agent in the production process of the composite material.
Furthermore, in addition to the dispersant, an adhesive and other additives are also added to the CNT nano-dispersion, in order to allow the CNTs to adhere to the surface of the base material.
Since CNTs adhere to the base material in the thus produced composite material, it is expected that the composite material will exhibit the original functions of the base material, and will also exhibit improved electrical conductivity, heat conductivity, mechanical strength and the like, which are derived from the CNTs.